Does knowledge gained with vipassana meditation arise spontaneously? It seems logical to me that it does, because it is not that knowledge that comes from concluding or thinking. I posed the question because I wanted to be sure. Thank you in advance for the answers.

My dictionary defines spontaneous as "occurring without external cause or incitement". This doesn't seem to fit, for the arising of insight depends upon encountering the Buddha's teaching (among other things).

Another definition given is "involuntary, not due to conscious volition". In this sense insight might be called spontaneous, for it cannot arise at any time when one is trying to make it arise.

It seems logical to me that it does, because it is not that knowledge that comes from concluding or thinking.

Insight knowledge doesn't come from these alone, but nor will it arise if we haven't done any concluding or thinking. Developing vipassana depends upon our first having developed understanding at the level of hearing (sutamaya) and thinking (cintamaya).

some like understanding nonself do 'pop up' suddenly. others are evident just on seeing patterns in phenomena- nama-rupa, cause and effect for example. Others are based on emotional reactions- like dukkha/unsatisfactoriness, fear, dissolution to what is going on. Others still require deeper 'drilling' into the subconsciousness- impermanence.